Alternating-current rectifier



Feb. 7, 1928.

L. B. MILLER ALTERNATING CURRENT RECTIF'IER Filed April 14, 1927 SIL /CO/V CARB/DE Inventar: Lew E5. Miller,

His Attorweg.

Patented Feb. 7, 192s.

UNITED STATES PATENT OFFICE.

LEVI B. MILLER, 0F LYNN, MASSACHUSETTS, ASSIGNOR TO GNERAL ELECTRIC COM- PANY', A. CORPORATION 0F NEW YORK.

ALTERNATING-CURRENT RECTIFIER.

Application lcd April 14, 1927. Serial No. 183,841.

My invention relates to alternating cui-,

rent rectitiers wherein current is transmitted between different solid materials maintained in juxtaposition with one another, and has for its principal object the provision of an improved dry rectifier which is stable in operation, does not deteriorate rapidly, and does not require preliminary operation or forming to establish the unilaterally conductive junction between the different solid materials.

Various types of apparatus have been utilized in the past to rectify the current transmitted between direct and alternating current circuits. Some of these apparatus comprise sheets or disks of different metals spaced apart by a very thin film of insulating material formed between them by subjecting them to an alternating voltage while they are pressed tightly together. These apparatus, as constructed in the past, have not been altogether satisfactory because they require preliminary operation lor forming, because they are unstable and deteriorate rapidly in use, or because a high pressure must be maintained between the materials both during formation of the insulation iihn and during the normal operation of the rectifier. In accordance with my invention, these objections are minimized or altogether avoided by theprovision of a rectilier which comprises layers of silicon carbide and graphite or carbon so joined together as to form a mechanically inseparable inass. Throughout the specification and claims, the expression carbonaceous material7 will be used to designate carbon, graphite. and materials having like characteristies. My invention will be better understood from the following description when considered in connection with the. accmnlmuying drawing and its scope will be. pointed out in the appended claims.

tet'erring to the drawings, Fig. 1 is a cross-section view of a rectifier constructed in accordance with my invention; and Fig. 2 is a wiring diagram of a rectifying system wherein my invention has been embodied.

rThe rectifier illustrated by Fig. 1 comprises a bolt l provided with nuts 3 and 4 and surrounded by an insulation sleeve 5 uponwhich are supported a plurality of rectifying elements each comprising a layer 6 of silicon carbide and a layer 7 of graphite, carbon or the like. In order to ensureV a good conductive connection between these rectifylng elements, they 4are spaced apart by disks 8 of lead orother soft metal which 1s readily pressed into intimate contact with their surfaces by means of the nuts 3 and 4.

Connections to the source of current supply are made through a terminal 9 and a terminal 10 which is insulated from the bolt 1 and nut 3 by the insulation sleeve 5 and an insulation washer 11. It has ,been found that current, .considered as flowing from positive to negative. is readily transmitted from the silicon carbide to the graphite but is transmitted .with great ditliculty in the reverse direction.y It should be understood that the particular structure illustrated is only one of the many forms in which my invention may be utilized.

Fig. 2 illustrates a system wherein an alternating current circuit 12 and a direct current device 13, such as a storage battery, are interconnected through a transformer 14, a smoothing reactor 15, and a pair of rectiers 16 and 17. With these connections, both halves of the alternating currentwave are rectified and fluctuation in the rectified current is minimized by the reactor 15.

The rectifying4 units 6-7 may be produced by subjecting graphite slabs to the vapors formed in a furnace containing fused quartz or other silicious materials such as -a mixture of quartz and carbon particles or a mixture of quartz and silicon carbide. By

this process, these vapors or their reduction products are brought into contact with a graphite slab and a tightly adhering layer' of silicon carbide is formed on the graphite..

The thickness of this layer is dependent both on the concentration of the vapors and on the duration of the treatment to which the. graphite is subjected and can be varied at will. but should not be made too thick for the reason that it increases the resist-ance of the rectifying unit. A layer having a thickness of approximately .02 inches has been found satisfactory for ordinary purposes. lt should be understood that the carbide coating ofthe graphite maybe produced not only by the vapor emanating from fused quartz but also by the deposition of the carbide itself from the vapor state or by the vapors emanating from heated carbides, oxycarbides and the like'.

The embodiment of the invention illustrated and described herein has been selected 2. An alternating current rectifier comprising a layer of graphite, and a layer 0f silicon carbide.

3. An alternating current rectifier comprising a layer of a carbonaceous material, and a layer of a carbide mechanically united with said layer of carbonaceous material.

4. An alternating current rectifier provided with an integral unit comprising a layer of graphite and a layer of silicon carbide.

In Witness whereof, I have hereunto set my hand this 12th day of April, 1927.

LEVI B. MILLER. 

